Abstract

We present the final data release from the GALEX Arecibo SDSS Survey
(GASS), a large Arecibo programme that measured the H I properties for
an unbiased sample of ˜800 galaxies with stellar masses greater
than 1010 M&sun; and redshifts 0.025 < z <
0.05. This release includes new Arecibo observations for 250 galaxies.
We use the full GASS sample to investigate environmental effects on the
cold gas content of massive galaxies at fixed stellar mass. The
environment is characterized in terms of dark matter halo mass, obtained
by cross-matching our sample with the Sloan Digital Sky Survey (SDSS)
group catalogue of Yang et al. Our analysis provides, for the first
time, clear statistical evidence that massive galaxies located in haloes
with masses of 1013-1014 M&sun; have at
least 0.4 dex less H I than objects in lower density environments. The
process responsible for the suppression of gas in group galaxies most
likely drives the observed quenching of the star formation in these
systems. Our findings strongly support the importance of the group
environment for galaxy evolution, and have profound implications for
semi-analytic models of galaxy formation, which currently do not allow
for stripping of the cold interstellar medium in galaxy groups.